1. Field of the Invention
The present invention relates to a plate clamping device of a printing machine, which is used when a plate is automatically charged to a plate carrier or the plate is automatically discharged from the plate carrier.
2. Description of the Related Art
Generally, an offset printing machine is provided with a cylindrical printing drum (plate carrier), in which a plate is wound around and charged to an outer circumferential surface of the printing drum, and a fore portion and a rear portion of the plate are clamped to the printing drum by using a plate clamping apparatus.
Conventionally, with regard to this kind of clamping apparatus, there is known, for example, an original sheet locking apparatus of a printing machine, which puts an end portion of a plate between a magnet plate and a clamping plate attracted by the magnet plate, and facilitates to discharge automatically the plate, described in the official gazette of Japanese Patent Laying Open (KOKAI) No. 61(1986)-104854.
Further, as a plate clamping apparatus which is suitable to charge the plate automatically, there is known, for example, an apparatus for clamping a printing plate onto a printing drum of a printing machine, which is constituted by incorporating a mechanism for clamping automatically a plate in the printing drum, or releasing the clamping, described in the official gazette of Japanese Patent Laying Open (KOKAI) No. 6(1994)-23955.
However, there is the following problems with regard to the conventional plate clamping apparatus as well as the above exemplified plate clamping apparatus.
First, in a case where an automatic charging and an automatic discharging are intended to be realized, the constructions of the plate clamping apparatus itself or the peripheral equipment become completed, so that a large-sizing and an increasing in cost of the whole printing machine are caused.
Secondly, the apparatus such as the above plate clamping apparatus incorporated into the printing drum is inferior in reliability so that a failure due to an entering of foreign matters is apt to be caused. In addition, this apparatus has unfavorable maintainability.